Cleanup machine based on the state in configuration file for mini installer test.

chrome/test/mini_installer/state_walker.py

+# Copyright 2017 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import re
+
+from file import File
+from registry import Registry
+from process import Process
+
+class StateWalker(object):
+  _TYPE_TO_ENTRY = {
+    'Files': File,
+    'Processes': Process,
+    'RegistryEntries': Registry,
+    }
+
+  def __init__(self, visitor):
+    self._visitor = visitor
+
+  def Walk(self, variable_expander, property_dict):
+    """Traverses |property_dict|, fetch data from OS and invoke |_visitor| in
+       the end."""
+    for property_name, property_value in property_dict.iteritems():
+      if property_name not in StateWalker._TYPE_TO_ENTRY:
+        raise KeyError('Unknown verifier %s' % property_name)
+      for entry_name, entry_value, in property_value.iteritems():
+         # Skip over expectations with conditions that aren't satisfied.
+        if 'condition' in property_value and not self._EvaluateCondition(
+            variable_expander.Expand(entry_value['condition'])):
+          continue
+        entry = StateWalker._TYPE_TO_ENTRY[property_name](variable_expander,
+            self._visitor)
+        entry.Check(entry_name, entry_value)
+
+  def _EvaluateCondition(self, condition):
+    """Evaluates |condition| using eval().
+
+    Args:
+      condition: A condition string.
+
+    Returns:
+      The result of the evaluated condition.
+    """
+    return eval(condition, {'__builtins__': {'False': False, 'True': True}})